Thanks for the reply.
Creating a separate instance for each ‘user’ doesn’t seem to scale well. If you have 100 users, then 100 instances? Or 100 databases? What if you had 1000 users - or more.
I did notice an old thread (2017) about modifying access to allow mutliple administrators to access other admins’ lists. See Multiple Owners for Subscriber Lists .
I haven’t dug into the code, but would a modification of the above mod allow a limitation on what an admin (not super-admin) sees? So that admin1 could create a list (and templates and more) that admin2 could not see or use?
His mod changes admin/accesscheck.php to return value based on the admin. Would a similar approach work? Is there a way to ‘filter’ all screens based on the admin user?